Declare which versions of Java are supported. Specifically, Java is n…

…o longer backwards compatible and built-in libraries such as javax/xml/bind/DataConverter have been removed in Java 9. I've actually added the following extra dependency to work around this:

implementation 'org.glassfish.jaxb:jaxb-runtime:2.3.2'

This is needed to provided the DataConverter class used by jlog.  JLog should really be fixing this though...

build.gradle

@@ -12,6 +12,11 @@ ext {
     releaseDate = 'Sep 22 2020'
 }
 
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
+
 repositories {
     jcenter()